#include <stddef.h>
#include <stdlib.h>
#include <ctype.h>
#include <string.h>
#include <printf.h>
//#include "base64.cpp"

static const char b64_table[] = {
        'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H',
        'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
        'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',
        'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
        'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
        'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
        'w', 'x', 'y', 'z', '0', '1', '2', '3',
        '4', '5', '6', '7', '8', '9', '+', '/'
};

#ifndef b64_malloc
#  define b64_malloc(ptr) malloc(ptr)
#endif
#ifndef b64_realloc
#  define b64_realloc(ptr, size) realloc(ptr, size)
#endif

/**
 * Encode `unsigned char *' source with `size_t' size.
 * Returns a `char *' base64 encoded string.
 */

char *b64_encode(const unsigned char *, size_t);

/**
 * Dencode `char *' source with `size_t' size.
 * Returns a `unsigned char *' base64 decoded string.
 */
unsigned char *b64_decode(const char *, size_t);

/**
 * Dencode `char *' source with `size_t' size.
 * Returns a `unsigned char *' base64 decoded string + size of decoded string.
 */
unsigned char *b64_decode_ex(const char *, size_t, size_t *);

char *b64_encode(const unsigned char *src, size_t len) {
    int i = 0;
    int j = 0;
    char *enc = NULL;
    size_t size = 0;
    unsigned char buf[4];
    unsigned char tmp[3];

    // alloc
    enc = (char *) b64_malloc(1);
    if (NULL == enc) { return NULL; }

    // parse until end of source
    while (len--) {
        // read up to 3 bytes at a time into `tmp'
        tmp[i++] = *(src++);

        // if 3 bytes read then encode into `buf'
        if (3 == i) {
            buf[0] = (tmp[0] & 0xfc) >> 2;
            buf[1] = ((tmp[0] & 0x03) << 4) + ((tmp[1] & 0xf0) >> 4);
            buf[2] = ((tmp[1] & 0x0f) << 2) + ((tmp[2] & 0xc0) >> 6);
            buf[3] = tmp[2] & 0x3f;

            // allocate 4 new byts for `enc` and
            // then translate each encoded buffer
            // part by index from the base 64 index table
            // into `enc' unsigned char array
            enc = (char *) b64_realloc(enc, size + 4);
            for (i = 0; i < 4; ++i) {
                enc[size++] = b64_table[buf[i]];
            }

            // reset index
            i = 0;
        }
    }

    // remainder
    if (i > 0) {
        // fill `tmp' with `\0' at most 3 times
        for (j = i; j < 3; ++j) {
            tmp[j] = '\0';
        }

        // perform same codec as above
        buf[0] = (tmp[0] & 0xfc) >> 2;
        buf[1] = ((tmp[0] & 0x03) << 4) + ((tmp[1] & 0xf0) >> 4);
        buf[2] = ((tmp[1] & 0x0f) << 2) + ((tmp[2] & 0xc0) >> 6);
        buf[3] = tmp[2] & 0x3f;

        // perform same write to `enc` with new allocation
        for (j = 0; (j < i + 1); ++j) {
            enc = (char *) b64_realloc(enc, size + 1);
            enc[size++] = b64_table[buf[j]];
        }

        // while there is still a remainder
        // append `=' to `enc'
        while ((i++ < 3)) {
            enc = (char *) b64_realloc(enc, size + 1);
            enc[size++] = '=';
        }
    }

    // Make sure we have enough space to add '\0' character at end.
    enc = (char *) b64_realloc(enc, size + 1);
    enc[size] = '\0';

    return enc;
}

unsigned char *b64_decode(const char *src, size_t len) {
    return b64_decode_ex(src, len, NULL);
}

unsigned char *
b64_decode_ex(const char *src, size_t len, size_t *decsize) {
    int i = 0;
    int j = 0;
    int l = 0;
    size_t size = 0;
    unsigned char *dec = NULL;
    unsigned char buf[3];
    unsigned char tmp[4];

    // alloc
    dec = (unsigned char *) b64_malloc(1);
    if (NULL == dec) { return NULL; }

    // parse until end of source
    while (len--) {
        // break if char is `=' or not base64 char
        if ('=' == src[j]) { break; }
        if (!(isalnum(src[j]) || '+' == src[j] || '/' == src[j])) { break; }

        // read up to 4 bytes at a time into `tmp'
        tmp[i++] = src[j++];

        // if 4 bytes read then decode into `buf'
        if (4 == i) {
            // translate values in `tmp' from table
            for (i = 0; i < 4; ++i) {
                // find translation char in `b64_table'
                for (l = 0; l < 64; ++l) {
                    if (tmp[i] == b64_table[l]) {
                        tmp[i] = l;
                        break;
                    }
                }
            }

            // decode
            buf[0] = (tmp[0] << 2) + ((tmp[1] & 0x30) >> 4);
            buf[1] = ((tmp[1] & 0xf) << 4) + ((tmp[2] & 0x3c) >> 2);
            buf[2] = ((tmp[2] & 0x3) << 6) + tmp[3];

            // write decoded buffer to `dec'
            dec = (unsigned char *) b64_realloc(dec, size + 3);
            if (dec != NULL) {
                for (i = 0; i < 3; ++i) {
                    dec[size++] = buf[i];
                }
            } else {
                return NULL;
            }

            // reset
            i = 0;
        }
    }

    // remainder
    if (i > 0) {
        // fill `tmp' with `\0' at most 4 times
        for (j = i; j < 4; ++j) {
            tmp[j] = '\0';
        }

        // translate remainder
        for (j = 0; j < 4; ++j) {
            // find translation char in `b64_table'
            for (l = 0; l < 64; ++l) {
                if (tmp[j] == b64_table[l]) {
                    tmp[j] = l;
                    break;
                }
            }
        }

        // decode remainder
        buf[0] = (tmp[0] << 2) + ((tmp[1] & 0x30) >> 4);
        buf[1] = ((tmp[1] & 0xf) << 4) + ((tmp[2] & 0x3c) >> 2);
        buf[2] = ((tmp[2] & 0x3) << 6) + tmp[3];

        // write remainer decoded buffer to `dec'
        dec = (unsigned char *) b64_realloc(dec, size + (i - 1));
        if (dec != NULL) {
            for (j = 0; (j < i - 1); ++j) {
                dec[size++] = buf[j];
            }
        } else {
            return NULL;
        }
    }

    // Make sure we have enough space to add '\0' character at end.
    dec = (unsigned char *) b64_realloc(dec, size + 1);
    if (dec != NULL) {
        dec[size] = '\0';
    } else {
        return NULL;
    }

    // Return back the size of decoded string if demanded.
    if (decsize != NULL) {
        *decsize = size;
    }

    return dec;
}

void encryptLong(uint32_t *firstChunk, uint32_t *secondChunk, uint32_t *key);

void decryptLong(uint32_t *firstChunk, uint32_t *secondChunk, uint32_t *key);

void encryptChar(char *buffer, int size, uint32_t *key);

void decryptChar(char *buffer, int size, uint32_t *key);

const char* teaDecrypt(char *key, char *source);

void encryptLong(uint32_t *firstChunk, uint32_t *secondChunk, uint32_t *key) {
    uint32_t y = *firstChunk;
    uint32_t z = *secondChunk;
    uint32_t sum = 0;

    uint32_t delta = 0x9e3779b9;

    //8轮运算(需要对应下面的解密核心函数的轮数一样)
    for (int i = 0; i < 32; i++) {
        sum += delta;
        y += ((z << 4) + key[0]) ^ (z + sum) ^ ((z >> 5) + key[1]);
        z += ((y << 4) + key[2]) ^ (y + sum) ^ ((y >> 5) + key[3]);
    }

    *firstChunk = y;
    *secondChunk = z;
}

void decryptLong(uint32_t *firstChunk, uint32_t *secondChunk, uint32_t *key) {
    uint32_t sum = 0;
    uint32_t y = *firstChunk;
    uint32_t z = *secondChunk;
    uint32_t delta = 0x9e3779b9;

    //32轮运算，所以是2的5次方；16轮运算，所以是2的4次方；8轮运算，所以是2的3次方
    sum = 0xC6EF3720;

    //8轮运算
    for (int i = 0; i < 32; i++) {
        z -= (y << 4) + key[2] ^ y + sum ^ (y >> 5) + key[3];
        y -= (z << 4) + key[0] ^ z + sum ^ (z >> 5) + key[1];
        sum -= delta;
    }
    *firstChunk = y;
    *secondChunk = z;
}

//buffer：输入的待加密数据buffer，在函数中直接对元数据buffer进行加密；size：buffer长度；key是密钥；
void encryptChar(char *buffer, int size, uint32_t *key) {
    char *p = buffer;
    int leftSize = size;
    while (p < buffer + size && leftSize >= sizeof(uint32_t) * 2) {
        encryptLong((uint32_t *) p, (uint32_t *) (p + sizeof(uint32_t)), key);
        p += sizeof(uint32_t) * 2;
        leftSize -= sizeof(uint32_t) * 2;
    }
}

//buffer：输入的待解密数据buffer，在函数中直接对元数据buffer进行解密；size：buffer长度；key是密钥；
void decryptChar(char *buffer, int size, uint32_t *key) {
    char *p = buffer;
    int leftSize = size;
    while (p < buffer + size && leftSize >= sizeof(uint32_t) * 2) {
        decryptLong((uint32_t *) p, (uint32_t *) (p + sizeof(uint32_t)), key);
        p += sizeof(uint32_t) * 2;
        leftSize -= sizeof(uint32_t) * 2;
    }
}

const char* teaDecrypt(char *key, char *source) {

    char *des = (char *)(b64_decode(source, strlen(source)));

    decryptChar(des, strlen(des), (uint32_t *)(key));

    return (const char*) des;
}